Coring apparatus



April 4, -1944. G. H.; FISHER CORING' APPARATUS Filed April 1, 1941 M 2 a a 6 m-4Y 3 m. a w Rw \w v R E? N f N. WH. SM m6 n M m s d M E., m m F H .wm Mm vm. r p F M h5 E11 I ELL l 9 5P P 2 3 w 2 2 W m N 2 rl Patented Apr. 4, 1944 coame APPARATUS Gordon II. Fisher, Dewey, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application April 1, 194.1, rseran No. 386,325

9 Claims.

This invention relates to coring and more particularly to apparatus for obtaining representative cores from subsurface formations.

It is common practice in the petroleum industry to obtain cores from hydrocarbon-bearing formations for the purpose of determining certain reservoir characteristics which are useful in predicting reservoir fluid performance. Virgin reservoirs may be cored usually with a. relatively high percentage of core recovery. Depleted formations at shallow depths may be cored with equal success. n the other hand, the coring of depleted reservoirs at greater depths yields a relatively low percentage of core recovery. In the present practice of caring, a drilling fluid is circulated downwardly through the drill pipe and thence upwardly through the annular space between the bore hole and the drill pipe to the surface of the ground where entrained formation cuttings are removed from the drilling fluid. As greater depths of formation are drilled or cored, the pressure of the drilling fluid column increases proportionately. In coring depleted hydrocarbon reservoirs, the pressure of the column of drilling fluid may become 'so great that the iluid and entrained formation cuttings will flow into the porous formation where the solid materials and the fluid will plug off the pore spaces otthe formation instead of circulating to the 'surface of the ground. If an unconsolidated formation is cored, drilling iluid under considerable pressure will wash away appreciable portions of the core so that which remains is non-representative of the formation cored. If a consolidated formation is cored, the drilling iluid may penetrate the core, contaminating the same. Non-representative or contaminated cores have little or no value yfor analytical interpretation.

By the practice of my invention, I am able to obtain representative formation cores, which are not contaminated by drilling iluid. The invention will be especially useful in coring low pressure and no -consolidated formations. as none of the high p1; ssure drilling uid which is used in conjunction with my apparatus comes in contact with the core or formation. Thus, contamination of the core or of the formation from which the core was cut, or other damage to the core which may also be caused by high pressure drilllng fluid, is eliminated.

My invention has for its primary object the provision of apparatus for obtaining represen-V tative cores from subsurface formations..

Another object of my invention is the provision of low pressure and non-consolidated formations.

A further object of my invention is the provision of apparatus for obtaining subsurface formation cores which are not contaminated with drilling fluid.

Still another object of my invention is the provision of apparatus for obtaining subsurface .formation cores by a reciprocating means.

These and additional objects and advantages will be apparent to personsk skilled in the art by reference to the following description and annexed drawing, wherein Figure 1 is an elevation view of one embodiment of my invention, partly in cross section; and l Figure 2 is an elevation View of another embodiment, partly in cross section.

Referring to Figure 1 of the drawing, I have denoted therein a bore hole I Il within which is is a string of tubing II extending downwardly from the surface of the ground (not shown). Connected to the lower extremity of the string of tubing is a housing, generally indicated by reference numeral I2 and consisting of a casting I3, a removable plug I4, and a member I5 that is threadedly connected to the lower end of the casting. The interior of the housing is bored on several diameters along a central longitudinal axisv to form an upper piston passage I6, a lower piston passage Il, a, drive head passage I8, and a drive stem passage I9. The casting is also provided with a iluid inlet duct 20, a fluid exhaust duct 2| and a fluid by-pass 22. From an examination of the drawing, it will be noted that fluid inlet duct 20 places the tubing string in communication with the juncture of lower piston passage Il and drive head passage I8; iluid exhaust duct 2l places upper piston passage I6 in communication with an exhaust conduit 23 that extends upwardly withinl the tubing string tothe surface of the ground; and fluid by-pass 22 establishes communication between piston passage I1 and the upper portion of piston passage I6.

A iluid actuated hammer or piston is contained within the housing and consists of a larger diameter portion 2l and a smaller diameter portion 28 that are arranged to reciprocate in and form effective fluid seals with upper piston passage I8 and lower piston passage Il, respectively. A drive head 26 is movable in passage I8 and forms an effective fluid seal therewith. The extreme upper end surface of the drive head is preferably somewhat smaller in area than the area of the lower end face of the piston. A stem 21 is slidable within passage I8 and is xdly connected to drive head 26 anda core barrel 28 that is provided with a plurality of cutting teeth 29 and a core catcher or retainer l0. While a core receptacle of the character illustrated is recommended in the practice of my invention, it will be obvious that various other known types of core receiving devices may be employed with equally satisfactory results.

For the purpose of outlining the mode of operation of the embodiment of the invention depicted in Figure 1, let us assume that the illustrated equipment is assembled and lowered into bore hole I so that core barrel 28 rests in the bottom thereof and drive head 26 is in the position shown. Due to the action of gravity, the hammer orpiston will rest on drive head 26. A high pressure uid, such as compressedI hydrocarbon gas, is now introduced into tubing string il from the surface of the ground from whence it passes through fluid inlet duct and acts against the lower end surface of the hammer to thereby move the hammer upwardly within the housing. When the hammer has moved a. predetermined distance upwardly, portion 26 thereof will cover the lower end of exhaust duct 2i. Continued upward movement of the hammer will uncover the lower end of by-pass 22, permitting fluid in passage il to flow through by-pass 22 and enter the upper part of passage I6, substantially equalizing the unit pressure at both ends of the hammer. Since the upper end surface area of the hammer is larger than its low end surface, it will be apparent that the total loading on the top of the hammer will be correspondingly greater than at the bottom. 'Ihe diierential in .total pressure and the force of gravity will therefore urge the hammer downwardly, causing it to strike drive head 26 and thereby force the core barrel downwardly into the formation. During its'downward stroke, the hammer rst covers the lower end of by-pass duct 22 and then uncovers the lower end of the exhaust duct, permitting the iiuid in passage it to be exhausted therefrom through exhaust duct 2i and exhaust conduit 23. By the time the hammer completes its downward stroke, the total fluid pressure load on the upper end surface thereof will be materially less than on its lower end surface. The fluid in inlet duct 2li then acts on the lower end of the hammer to again raise it upwardly and the above outlined cycle is repeated. It will be evident that each impact of the hammer against the drive headis directly dependent upon the unit pressure of the actuating fluid and the difference in area of the extreme end surfaces of the hammer. It is therefore a mere matter of design to obtain the desired impact on each stroken of the hammer. In order to prevent ,injury to the equipment, the tubing string is advancedvor fed" downwardly into the bore hde as the core barrel is driven into the formation. When the core barrel has penetrated the formation to a requisite distance, the supply of fluid to the housing is cut off and `he entire assembly is withdrawn from the bore ole.

It is to be borne in mind that, if desired, inner conduit 23 may be connected to the upper end of inlet duct 20, thereby placing exhaust duct 2| in direct communication with tubing string Il. With this arrangement, high pressure uid is transmitted into the housing through conduit 23 and inlet duct 20, while fluid, so introduced into the housing, is exhausted therefrom through exhaust duct 2l and tubing string i I.

' A second embodiment of my invention is shown in Figure 2 wherein like parts of this and the first embodiment are denoted by the same reference numerals. This embodiment is adapted to be employed in obtaining cores through bore holes that are provided with casing 3l which forms an annular space 32 with tubing string Il and housing I2a. Fluid exhaust duct 2|a communicates with annular space 32 ln this instance instead of through the exhaust conduit 23 of Figure 1. A suitable packer 33- is posi- 4tionecl in the annular space between the casing and the housing at a depth below the juncture of the exhaust port and the annular space. Except for the above enumerated differences in construction, the apparatus of the second embodiment of the invention is identical with that of the first described embodiment.

The operation of the second embodiment of my invention is likewise the same as that of the rst embodiment except that the fluid is exhausted upwardly through annular space t2 instead of through conduit 23.

It is to be understood that the forms of myy invention, herewith shown and described, are to be taken as preferred examples of the same, and

that various changes in shape, size and arrangement of parts may be resorted to without departing from the spirit of my invention, or the scope of the subioined claims.

I claim:

1. In apparatus of the character described, the combination comprising a core receiving recoptacle adapted to be lowered into a bore hole, a housing, a drive head reciprocably disposed within the housing and connected to the core receptacle, a fluid actuated hammer within the housing for imparting a thrust to the drive head to urge the core receptacle into the formation at the bottom of the 'bore hole, a conduit in the Abore hole for transmitting an actuating uid at superatmospheric pressure into the housing, and means for exhausting actuating fluid from the housing.

2. In apparatus of the character described, the combination comprising a core receiving receptacle adapted to be lowered to the bottom of a well bore, a housing extending above the 'receptacle and substantially fixedly positioned in the well bore, a member reciprocable in the housing and secured to the receptacle, and fluid actuated means within the housing and reciprocable independently of the member for imparting a thrust to the member to urge the core receptacle downwardly into the formation at the bottom of the well bore without downward movement of the housing.

3. In apparatus of the character described, the combination comprising a housing adapted to be lowered into a well bore, a core receiving receptacle below the housing and movable with respect thereto, a member slidable in the housing and secured to the receptacle, and a fluid actuated hammer within the housing for imparting a downward thrust to the member to urge the core receptacle downwardly into the formation at the bottom of the well bore without downward movement of the housing.

4. In apparatus of the character described, the combination comprising a pressure uid conduit adapted to be substantially xedly disposed in a well bore, a housing secured to the lower end of the conduit, a core receiving receptacle extending below the housing,a` member reciprocable in the housing and secured to the receptacle, and

a hammer reciprocable independently of the member within the housing and actuated by pressure fluid transmitted thereto by the conduit for imparting a thrust to the member to urge the core receptacle downwardly into the formation at the bottom of the well bore without downward movement of the housing.

5. In apparatus of the character described, the combination comprising a pressure fluid conduit adapted to be substantially iixedly disposed in a well bore, a housing secured to the lower end of the conduit, a core receiving receptacle exterior the housing and disposed therebelow, a member reciprocable in the housing, means for connecting the member to the receptacle, and a hammer independently reciprocable with respect to the member within the housing and actuated by fluid pressure transmitted thereto by the conduit for imparting an impact thrust to the member to drive the core receptacle downwardly into the formation at the bottom of the well bore without downward movement of the housing.

6. In apparatus of the character described, the combination comprising a core receiving receptacle adapted to be lowered into a bore hole, a housing, a drive head reciprocably disposed within the housing and connected to the core receptacle, a Auid actuated hammer within the housing for imparting a thrust to the drive head to urge the core receptacle into the formation at the bottom of the bore hole, a conduit in the bore hole for transmitting an actuating fluid at superatmospheric pressure into the housing, and a conduit within the first conduit for exhausting actuating uid from the housing.

7. In apparatus of the character described, the combination comprising a. core receiving receptacle adapted to belowered into a bore hole, a housing, a drive head reciprocably disposed within the housing and connected to the core receptacle, a uid actuated hammer within the housing for imparting a thrust to the drive head to urge the core receptacle into the formation at the bottom of the bore hole, a conduit in the bore hole for transmitting an actuating fluid at superatmospheric pressure into the housing, and a conduit exterior the rst conduit for exhausting actuating fluid from the housing.

8. In apparatus of the character described, the combination comprising a conduit in a bore hole, a core receiving receptacle adapted to be lowered through the conduit to the bottom of the bore hole, a housing, fluid actuated means Within the housing for driving the core receptacle into the formation at the bottom of the bore hole, a conduit for transmitting actuating fluid at superatmospheric pressure into the housing, said last mentioned conduit being disposed within the first mentioned conduit and forming an annular space therewith, uid exhaust means establishing communication between the interior of the housing and the annular space, and packer means in the annular space below the juncture of the fluid exhaust means and the annular space.

9. In apparatus of the character described, the combination comprising a conduit in a bore hole, a core receiving receptacle adapted to be lowered through the conduit to the bottom of the bore hole, a housing, a drive head reciprocably disposed vvithin the housing and connected to the core receptacle, a fluid actuated hammer within the housing for imparting a thrust to the drive head to urge the core receptacle into the formation at the bottom of the bore hole, a conduit for transmitting actuating fluid at supera'tmospheric pressure into the housing, said last mentioned conduit being disposed within the first mentioned conduit and forming an annular space therewith, fluid exhaust means establishing communication between the interior of the housing and the annular space, and a packer in the annular space below the juncture of the fluid exhaust means and the annular space.

GORDON H. FISHER. 

